The benefits of using silicone-coated compositions over organic polymer coating compositions on textile fabrics, include improved weatherability, ability to maintain flexibility and heat resistance of the coated textile fabrics.
Coating textile fabrics with silicone rubber may impart a variety of benefits to the coated fabric used in automotive air bags. For example in EP 553,840, Nakamura et. al describe a liquid silicone rubber coating composition for application to automotive airbags, which comprises polydiorganosiloxane having alkenyl groups, an polyorganosiloxane resin, an inorganic filler, a polyorganohydrogensiloxane, a platinum group metal catalyst, and an epoxy group-containing organosilicon compound. In EP 646,672, MaGee et. al describe a fabric impregnated with a silicone composition comprising a linear polyorganosiloxane having aliphatic unsaturation, a certain polyorganohydrogensiloxane, a catalyst promoting addition reaction, a hydrophobic silica, a flame inhibitor, and optionally an adhesion promoting agent. The latter publication also suggests the use of the composition for fabrics used in the construction of airbags.
It is often desirable to provide coated textile fabrics with a finish which is relatively smooth and free of surface tack. A particular example relates to the use of coated textile fabrics in the manufacture of airbags for use in automobiles. When such airbags are deployed, due to the use of an explosive charge, friction is inevitable. Such friction takes place where textile rubs over textile, and also where textile comes into contact with the interior of the automobile or a driver or passenger in an automobile during or after deployment. The amount of friction created can in some circumstances slow down the deployment of the airbag or cause burns to the skin of the driver or passenger. Therefore it is desirable to provide coated textile fabrics for use in automotive airbags which have a relatively low coefficient of friction.
In EP 0712956, Saitoh et. al describe a coating composition for a fabric, comprising a rubber component, a solvent, and a powder of an inorganic compound or an organic compound having an average particle size of from 0.5 to 20 .mu.m, preferably at 20 to 50 parts by weight, per 100 parts of the rubber component. The coating composition is said to improve the feeling of a rubber coated film by eliminating the sticky feeling of the rubber coated film. Examples of the inorganic or organic powders are aluminium hydroxide, mica, polymethyl-silsesquioxane, carbon, polyamide and polyfluoroethylene. Preferred powders are spherical, as a flaky powder is said to be liable to weaken the rubber properties. Particles with an average size over 20 .mu.m are stated as giving a poor coating property. The presence of a solvent is indicated to be very important, as it has a function of uniformly spreading the powder.
Solvents are preferably avoided in the coating industry in general. However, a drawback of some solventless silicone rubber compositions is that when coated onto fabrics the surface of the applied film presents some residual tack even after cure of the silicone rubber. When left as is, this residual tack impairs the processability during such operations as sewing and also causes adjacent films of the coating to stick to each other during storage of the folded fabric. These problems have made it necessary to dust the surface of the applied films with, for example, talc, calcium carbonate, or clay.
Nakamura et al. in U.S. Pat. No. 5,789,084 describe a curable liquid silicone rubber coating composition including (A) 100 pts. by weight of a polydiorganosiloxane that contains at least 2 alkenyl groups in each molecule; (B) 5 to 100 pts. by weight of polyorganosiloxane resin; (C) 5 to 100 pts. by weight of an inorganic filler; (D) an polyorganohydrogensiloxane that contains at least 2 silicon-bonded hydrogen atoms in each molecule in a quantity that affords a value from 0.6:1 to 20:1 for the ratio of the number of moles of silicon-bonded hydrogen in this component to the number of moles of alkenyl in component A; (E) a platinum group catalyst in a quantity that affords 0.1 to 500 weight parts platinum group metal for each one million weight pts. component (A); (F) 0.1 to 20 weight parts of an epoxy-functional organosilicon compound; and (G) 0.1 to 5 weight parts an organotitanium compound. This composition can be used for thin coatings on synthetic fabrics, without using a dilution solvent.